The White Helmets is a Netflix documentary nominated for an Academy Award for Best Documentary, Short Subject. According to the AP, the film’s cinematographer, Khaled Khatib, will not be permitted to enter the United States to attend the ceremony after authorities found “derogatory information” during his background check.

The AP reports that it reviewed internal documents in which the Department of Homeland Security decided to block the cinematographer from flying to Los Angeles. Khatib had obtained a visa to enter the US, but had been detained earlier this week in Turkey for unknown reasons. “Derogatory information” is an umbrella term that can “include anything from terror connections to passport irregularities,” according to the news service.

According to documents, Khatib needed a passport waiver to enter the country, which was not issued. DHS declined to comment on the case to the AP, simply noting that "a valid travel document is required for travel to the United States."

In a post to Twitter, Khatib noted that he would not attend the ceremonies “due to intensity of work, our priority is helping our people.”

Khatib was the Press Officer for the Syrian Civil Defense, and joined the project in 2015 after meeting the film’s director, Orlando von Einsiedel. He shot much of the footage in the documentary, which follows the operations of the volunteer rescue workers, known for the white helmets that they wear. The group was nominated for a Nobel Peace Prize in 2016.

Speaking to CNN, Khatib noted that he was proud of the work on the film, and noted that if the film won, it would “show people across Syria that people around the world support them. It will give courage to every volunteer who wakes up every morning to run towards bombs.”

An executive order from President Donald Trump issued in January temporarily blocked travel from seven majority-Muslim countries. While several federal courts halted the implementation of the order, there have been several high-profile instances where foreign travelers have faced issues entering the country.

Update, February 26th, 2017: In response to Khatib being barred from entering the US, the Syrian Civil Defense announced that they would boycott the ceremony:

“The Syria Civil Defence will not be attending the Oscars in Los Angeles.

“Raed Saleh, Head of the Syria Civil Defence  is the holder of US visa. Raed was planning to attend but can not make it, the intense air strikes across the country mean he must focus on work inside Syria.

“Khaled Khatib, a Syria Civil Defence volunteer and cameraman on the film, was due to attend. Unfortunately Khaled Khatib was not able to travel to the Oscars due to his passport being cancelled by the Syrian regime, despite having been issued a US visa specifically to attend the awards ceremony.

“The Syria Civil Defence are grateful for the platform the film ‘The White Helmets’ is providing for their humanitarian message to reach around the world.

“The Syria Civil Defence wants to thank all the people around the world that have sent messages of support for their Oscar nomination.”